As anyone who has ever played and enjoyed the game of golf can relate, the sport has a great propensity to both simultaneously enthuse and frustrate. The seemingly simple task of swinging a golf club and hitting a golf ball is not at all simple, and in fact, the dynamics of properly hitting a golf ball are quite complex. The most desirable ball flight characteristics generally occur when the golf ball is struck with the "sweet spot" on the face of the club head, maximum impact and true flight occurring at that location. For a variety of reasons, it is often extremely difficult for a golfer to overcome his or her propensity to strike the golf ball at a point on the club head face that is not in alignment with the sweet spot, or center of mass of the club head. Even the best golfer may be unable to overcome a particular glitch in his or her swing that causes a recurring "hook" or "slice" or other unwanted ball trajectory, and it is especially true that the typical golfer will tend to hook the ball with the shorter clubs and slice with the longer ones. And even where the one problem is solved, another invariably rises to take its place. The foregoing is evidenced in the great inconsistency with which professional golfers win tour competitions, as well as in the rise of high-tech services that offer sophisticated sensor feedback and computer analysis in order to assist a golfer in correcting a problematic swing.
A number of prior attempts have been made in an effort to increase a golfer's ability to properly hit a golf ball. A common focus has been on the redistribution of weight across the back of the golf club head. So-called "perimeter weighting" provides a larger sweet spot and thus tends to be more forgiving when the ball is not struck in precise alignment with the center of mass of the club head. Still, the golfer is at the mercy of a sweet spot that has been designated by the club maker. If the golfer's average or usual contact point with the ball is away from the sweet spot, this arbitrary sweet spot is in the wrong place, and the average hit will not feel as good to the golfer as it might otherwise. Fixed perimeter weighting assumes a golfer's average swing is on the swing spot. It rarely is.
Thus, in addition to perimeter weighting, it is desirable to be able to change (move) the actual center of mass and, therefore, the sweet spot of the club head. Towards this end, a number of designs for weight balancing a club head have been proposed. Some of these designs, such as that shown in U.S. Pat. No. 5,026,056 issued on Jun. 25, 1991 to McNally et al., incorporate integral, fixed or otherwise permanent weights that are positioned to provide a sweet spot that correlates with the visual center of the club face. Such a design, while to some extent a helpful assist, is inflexible and does not permit the weighting of the club to be tuned to the swing of the individual golfer. And even where a fixed-weight club is customized for the individual, as noted, a golfer's swing is generally not a static phenomenon but rather changes, if only for temporary, frustrating periods of time.
Much better, then, are designs that permit adjustable weight balancing. A number of patents have issued for weighting schemes that share in common the characteristic of employing chambers that are drilled or hollowed at various angles into either an iron or a wood club head. See for example U.S. Pat. No. 4,867,458 issued on Sep. 19, 1989 to Sumikawa et al., U.S. Pat. No. 4,607,846 issued on Aug. 26, 1986 to Perkins, U.S. Pat. No. 4,145,052 issued on Mar. 20, 1979 to Janssen et al., and U.S. Pat. No. 3,979,122 issued on Sep. 7, 1976 to Belmont. A weight, in the form of a threaded screw, plug or metal powder, is inserted into a chamber and positioned to achieve the desired weighting and balance. These methods are clumsy and awkward to implement, and achieving a proper adjustment is not intuitively simple. The latter is especially true in light of the fact that it would appear to be difficult for the golfer to tell by visual observation alone the degree or extent to which any adjustment has been made by the aforementioned methods, the positioning of the weights being made within hidden recesses and/or there being no simple guide or reference markers that can be employed during adjustment.
Shown in U.S. Pat. No. 3,199,874, issued on Aug. 10, 1965 to Blasing, is a variable weighting system for a wood-type club head. Here there is provided a rotatable turntable within the club head which includes a cavity for containment of a quantity of elemental mercury. The cavity is configured to provide an eccentric weighting capability, wherein a greater quantity of mercury pools in the cavity at a distance removed from, rather than nearer to, the center of the turntable. With a hold down screw loosened, the golfer simply rotates the turntable (by moving an indicator prong on the upper surface of the club head) to reposition a heavier mass of mercury heelward or toeward to correct either a hook or slice, respectively. The rushing movement of the mercury toward the club face at impact with a golf ball also provides additional force impetus to the ball. While implementation of the described weighting feature is simple and adjustment is intuitive, modern day commercial use of the invention is highly problematic (if not illegal) because of the extreme health hazard presented by mercury and because its use and disposal are now so highly regulated. Moreover, because of the dynamic nature of the mercury, this type of club head would not be allowed for professional use by the United States Golf Association (U.S.G.A.).
In a further effort to increase the golfer's ability to properly hit the ball, golf club manufacturers have for some time also offered golf clubs with so-called "oversized" club heads. An oversized club lead, in similar fashion to a club head with perimeter weighting, provides that a larger sweetspot is available such that the golf ball need not be struck precisely in alignment with the center of mass of the club head in order to achieve a tolerable shot. However, because the shapes of traditional club heads are not symmetrical, but are rather "pear" shaped in the case of woods, and "wedge" shaped in the case of irons, or of some otherwise unsymmetrical shape, and because golf club manufacturers have continued to adhere to these traditional golf club shapes in the production of oversized golf clubs, such oversized golf clubs as are presently made do not take full advantage of the increased club head size.
In particular, as the club head size becomes larger, the center of mass moves farther and farther away from the golf club shaft. This makes a draw harder to hit, and actually promotes a fade. In the case of woods, for example, an oversized, pear-shaped club head means that a relatively large area behind and back of the golf club shaft is not as fully weighted as it might otherwise be were the center of mass brought back to a location less removed from the shaft where an even greater area of an already increased sweetspot would be caused to be made available, thus obtaining greater control and a more favorable ball flight trajectory.
Because of the limitations associated with most presently available golf clubs, a substantial need still exists for a golf club that provides for an intuitively simple, efficient and easy method of weight balance adjustment. It would further be extremely desirable to provide for an oversized club head which offers a better weight distribution, preferably one into which such a simple method of weight balance adjustment might also be incorporated.